Ballism is defined as a movement disorder characterized by involuntary, forceful, flinging, high-amplitude “throwing” movements. Ballism is often accompanied by choreatic movements, the latter being more distal whereas ballism describes the proximal movements. With time, the proximal ballistic movements may become less pronounced, and the distal choreatic movements predominate. Ballism increases with action and is absent during sleep. The movements can be so violent that patients injure themselves. Ballism usually affects one side of the body, and it is then referred to as hemiballism. Older terms are hardly ever used anymore – that is, monoballism if only one limb is affected, biballism if both extremities on one side of the body but not the head or face are affected, or paraballism if both sides of the body are affected.

This chapter discusses the clinical approach to a patient with a movement disorder, based on the phenomenology of that particular disorder. It summarizes the definitions of the most prevalent movement disorders and highlights particular clinical aspects that may help narrow down the differential diagnosis.

Movement disorders are rarely medical emergencies or reason for evaluation in the emergency department (ED). However, they may be seen, and range from the familiar parkinsonism and drug-induced dystonia to rare disabling hemiballism secondary to a stroke. Movement disorders are typically a sign of an underlying neurological or nonneurological disorder, rather than the primary diagnosis. They can be strange in appearance and are often misdiagnosed as being hysterical or psychiatric in origin. In the ED, movement disorders are diagnosed based on a history and physical examination, with relatively few contributions from laboratory and radiographic studies.